GT911 Touch Controller

The Gt911 class provides an interface to the GT911 touch controller.

GT911 Example
- How to use example
- Example Output

API Reference

Header File

components/gt911/include/gt911.hpp

Classes

class Gt911 : public espp::BasePeripheral<std::uint16_t>

Driver for the GT911 touch controller.

Example

    // make the I2C that we'll use to communicate
    espp::I2c i2c({
        .port = I2C_NUM_0,
        .sda_io_num = (gpio_num_t)CONFIG_EXAMPLE_I2C_SDA_GPIO,
        .scl_io_num = (gpio_num_t)CONFIG_EXAMPLE_I2C_SCL_GPIO,
        .sda_pullup_en = GPIO_PULLUP_ENABLE,
        .scl_pullup_en = GPIO_PULLUP_ENABLE,
        .timeout_ms = 100,
        .clk_speed = 400 * 1000,
    });

    bool has_gt911_5d = i2c.probe_device(0x5d);
    bool has_gt911_14 = i2c.probe_device(0x14);
    uint8_t address = has_gt911_5d ? 0x5d : 0x14;
    fmt::print("Touchpad probe: {}\n", has_gt911_5d || has_gt911_14);
    fmt::print("       address: {:#02x}\n", address);

    // now make the gt911 which decodes the data
    espp::Gt911 gt911({.write = std::bind(&espp::I2c::write, &i2c, std::placeholders::_1,
                                          std::placeholders::_2, std::placeholders::_3),
                       .read = std::bind(&espp::I2c::read, &i2c, std::placeholders::_1,
                                         std::placeholders::_2, std::placeholders::_3),
                       .address = address,
                       .log_level = espp::Logger::Verbosity::WARN});

    // and finally, make the task to periodically poll the gt911 and print
    // the state
    auto task_fn = [&gt911](std::mutex &m, std::condition_variable &cv) {
      std::error_code ec;
      // update the state
      bool new_data = gt911.update(ec);
      if (ec) {
        fmt::print("Could not update state\n");
        return false;
      }
      if (!new_data) {
        return false; // don't stop the task
      }
      // get the state
      bool home_pressed = false;
      home_pressed = gt911.get_home_button_state();
      fmt::print("home_pressed: {}\n", home_pressed);
      uint8_t num_touch_points = 0;
      uint16_t x = 0, y = 0;
      gt911.get_touch_point(&num_touch_points, &x, &y);
      if (ec) {
        fmt::print("Could not get touch point\n");
        return false;
      }
      fmt::print("num_touch_points: {}, x: {}, y: {}\n", num_touch_points, x, y);
      // NOTE: sleeping in this way allows the sleep to exit early when the
      // task is being stopped / destroyed
      {
        std::unique_lock<std::mutex> lk(m);
        cv.wait_for(lk, 50ms);
      }
      return false; // don't stop the task
    };
    auto task = espp::Task({.callback = task_fn,
                            .task_config = {.name = "Gt911 Task"},
                            .log_level = espp::Logger::Verbosity::WARN});
    task.start();

Public Types

typedef std::function<bool(uint8_t)> probe_fn

Function to probe the peripheral

Param address: The address to probe
Return: True if the peripheral is found at the given address

Public Functions

inline explicit Gt911(const Config &config)

Constructor for the GT911 driver.

Parameters: config – The configuration for the driver

inline bool update(std::error_code &ec)

Update the state of the GT911 driver.

Parameters: ec – Error code to set if an error occurs
Returns: True if the GT911 has new data, false otherwise

inline uint8_t get_num_touch_points() const

Get the number of touch points.

Note

This is a cached value from the last update() call

Returns: The number of touch points as of the last update

inline void get_touch_point(uint8_t *num_touch_points, uint16_t *x, uint16_t *y) const

Get the touch point data.

Note

This is a cached value from the last update() call

Parameters

num_touch_points – The number of touch points as of the last update
x – The x coordinate of the touch point
y – The y coordinate of the touch point

inline bool get_home_button_state() const

Get the home button state.

Note

This is a cached value from the last update() call

Returns: True if the home button is pressed, false otherwise

inline bool probe (std::error_code &ec) requires(true)

Probe the peripheral

Note

This function is thread safe

Note

If the probe function is not set, this function will return false and set the error code to operation_not_supported

Note

This function is only available if UseAddress is true

Parameters: ec – The error code to set if there is an error
Returns: True if the peripheral is found

inline void set_address (uint8_t address) requires(true)

Set the address of the peripheral

Note

This function is thread safe

Note

This function is only available if UseAddress is true

Parameters: address – The address of the peripheral

inline void set_probe (const probe_fn &probe) requires(true)

Set the probe function

Note

This function is thread safe

Note

This should rarely be used, as the probe function is usually set in the constructor. If you need to change the probe function, consider using the set_config function instead.

Note

This function is only available if UseAddress is true

Parameters: probe – The probe function

inline void set_write(const write_fn &write)

Set the write function

Note

This function is thread safe

Note

This should rarely be used, as the write function is usually set in the constructor. If you need to change the write function, consider using the set_config function instead.

Parameters: write – The write function

inline void set_read(const read_fn &read)

Set the read function

Note

This function is thread safe

Note

This should rarely be used, as the read function is usually set in the constructor. If you need to change the read function, consider using the set_config function instead.

Parameters: read – The read function

inline void set_read_register(const read_register_fn &read_register)

Set the read register function

Note

This function is thread safe

Note

This should rarely be used, as the read register function is usually set in the constructor. If you need to change the read register function, consider using the set_config function instead.

Parameters: read_register – The read register function

inline void set_write_then_read(const write_then_read_fn &write_then_read)

Set the write then read function

Note

This function is thread safe

Note

This should rarely be used, as the write then read function is usually set in the constructor. If you need to change the write then

Parameters: write_then_read – The write then read function

inline void set_separate_write_then_read_delay(const std::chrono::milliseconds &delay)

Set the delay between the write and read operations in write_then_read

Note

This function is thread safe

Note

This should rarely be used, as the delay is usually set in the constructor. If you need to change the delay, consider using the set_config function instead.

Note

This delay is only used if the write_then_read function is not set to a custom function and the write and read functions are separate functions.

Parameters: delay – The delay between the write and read operations in write_then_read

inline void set_config(const Config &config)

Set the configuration for the peripheral

Note

This function is thread safe

Note

The configuration should normally be set in the constructor, but this function can be used to change the configuration after the peripheral has been created - for instance if the peripheral could be found on different communications buses.

Parameters: config – The configuration for the peripheral

inline void set_config(Config &&config)

Set the configuration for the peripheral

Note

This function is thread safe

Note

The configuration should normally be set in the constructor, but this function can be used to change the configuration after the peripheral has been created - for instance if the peripheral could be found on different communications buses.